Scientists at Cambridge University believe that not being able to recall past events accurately is more likely to result from the brain forming incomplete memories that are easily confused over time.
The findings, which could lead to new treatments, turn traditional theories of forgetfulness on their head and suggest that making greater – more conscious – efforts to remember things in the first place could help dementia patients.
Dr Lisa Saksida, from the Department of Experimental Psychology at the University of Cambridge, said: "This study suggests that a major component of memory problems may actually be confusion between memories, rather than loss of memories per se.
"This is consistent with reports of memory distortions in dementia – for example, patients may not switch off the cooker, or may fail to take their medication, not because they have forgotten that they should do these things, but because they think they have already done so."
Currently, memory problems are typically perceived to be the result of forgetting previously encountered items or events, the study said.
But the new research found that the ability of the brain to maintain complete, detailed memories is more likely disrupted.
The remaining, less detailed memories are relatively easily confused, leading to an increased likelihood of falsely remembering information that was not encountered.
Previous research on memory found that animals genetically engineered to suffer dementia could not tell whether an object was familiar or not.
But they did not demonstrate whether the animal was unable to distinguish between the objects because it has forgotten it had seen it before, or it created a false memory of being familiar with the object.
In order to examine which is indeed the case, the researchers developed a new experimental method that allows them to analyse responses to the new and the old objects separately.
Animals were allowed to look at an object and then, after an hour, were given a memory test in which they were either shown the same object again, or a new object.
Normal animals spent more time exploring the new object, indicating that they remembered and were familiar with the old object.
But animals with amnesia performed poorly on the memory task, as they spent an equal amount of time exploring the old and the new object.
The amnesic animals explored the new object less than the normal animals did, indicating false memory for the new object.
The researchers then looked at ways to improve memory.
To do this, they placed the animals in a dark, quiet space – rather than the usual busy environment – before the memory test.
Amnesic animals who showed no recollection when they spent the time before the memory test in normal, busy conditions, showed perfect memory when they spent the time before the memory test in a dark, quiet environment.
Dr Saksida continued, “One thing that we found very surprising about our results was the extent of the memory recovery, achieved simply by reducing the incoming information prior to the memory test."
The findings are published today in the journal Science.